CSS-based Exfiltration Vulnerability in Mozilla Thunderbird
CVE-2026-0818

4.3MEDIUM

Key Information:

Vendor

Mozilla
Status
Thunderbird
Vendor
CVE Published:
28 January 2026

What is CVE-2026-0818?

This vulnerability pertains to Mozilla Thunderbird, where an attacker can exploit CSS-based techniques to exfiltrate content from partially encrypted emails if remote content is allowed. Users running versions below 147.0.1 and 140.7.1 are particularly at risk, making it essential to implement updates to safeguard against this security flaw.

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Affected Version(s)

Thunderbird < 147.0.1

Thunderbird < 140.7.1

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1881530
https://www.mozilla.org/security/advisories/mfsa2026-07/
https://www.mozilla.org/security/advisories/mfsa2026-08/

CVSS V3.1

Score:
4.3
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Leon Trampert, Daniel Weber, Christian Rossow, Michael Schwarz
JSON
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